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The Arsenal: Building An Assault Rifle

November 3, 2013

East German soldiers cleaning their weapons.

As a noted historian once declared, it’s by studying weapons that we understand the political structures governing our lives.

For this post, the author will focus on the AK-47, the world’s best and most ubiquitous assault rifle. More than 60 years since it entered mass production, the AK-47 has spawned dozens of variants and formed the basis for several other rifles used by national armies.

What qualities made the AK-47 so popular and deadly?

Let’s examine how it works. As simple as its functions are, to produce a rifle similar to the AK-47 requires a substantial investment.

Both time and money (and patience) are required for the task of making a single assault rifle, more so when vast industrial resources and the proper equipment are unavailable.

Here is what it takes to create an AK-47.

Via RIA Novosti

Via RIA Novosti

Tools

It would be easier to have a well-equipped factory at one’s disposal. But owing to its ruggedness, an AK-47 can be built with a little know-how and a decent workshop. A few essentials:

1. Work Bench
2. Drill Press
3. Hydraulic Press
4. Vice
5. Rectangular Die
6. A Spot Welder and a Blowtorch
7. Bolt Cutter
8. Ball-peen Hammer
9. Bending Jig
10. Riveting Jig
11. Rivet Driving Tool
12. Steam Table Pan three (3) feet long
13. Drill
14. Digital Caliper
15. Lathe
16. Threading Machine

The Mighty Riveting Jig.

The Riveting Jig.

AK47 v2.1

Assembled. (For precise specifications, Google other sources.)

Getting To Know It

The AK-47 is basically 32 inches of steel and wood. Today polymer parts and accessories are available but steel and wood are often the starting material for most AK’s.

Not just any steel, however. Sure, aluminum and scrap metal are just as suitable, but unless the right grade is what’s used–like 4140 chrome molybdenum steel, for example–their long-term durability is a question mark.

The AK-47 disassembled for cleaning has seven removable parts. But when it comes to what holds an AK-47 together, there are 69 different pieces involved.

AK47 schematic

But this schematic lists 82. What?

The essential part of the AK-47 is the steel receiver. This 10-inch rectangular housing supports the pistol grip, the trigger assembly, the magazine well, the trunnion, and the fire selector switch.

As mundane as it appears, the AK-47’s receiver has a storied existence. The first AK-47’s were milled. Molten steel was poured in a mold and hardened to its intended form. Milled receivers and parts are often commended for their sturdiness.

For greater efficiency, the Soviets developed the stamped receiver. A thin sheet of steel was taken and cut according to spec. Holes were drilled to fit rivets and the various mechanical parts. The sheet was then attached to a rectangular die and bent to its desired “U” shape. The AKM is an evolved AK-47 with a stamped receiver and a simple pointed muzzle brake, also known as a slant compensator.

The AK-47 stamped steel receiver before shaping.

The AK-47 stamped steel receiver before shaping.

Stamped Receiver plate. Note how the front end is narrower than the back, where larger hales have been drilled to support an underfolding metal stock. The edges have also been curved to better fit the Dust Cover.

Stamped Receiver plate. Note how the front end is narrower than the back, where larger holes have been drilled to support an underfolding metal stock. The edges are curved to better fit the Dust Cover.

Another feature of note in the AK-47’s receiver is the ingenious fire selector that doubles as its safety. Simply switching the fire selector down changes the rate of fire.

AK47 fire selector

Above the receiver is the curved dust cover protecting the chrome-plated bolt carrier and the recoil spring. The bolt carrier connects to the sight block while the bolt itself is aligned with the trunnion. Above the trunnion is the flip sight, which aligns with the front sight at the end of the muzzle.

AK-47 rear sight

AK-47’s usually have wooden furniture, i.e. the butt stock, the pistol grip, and the hand guards/heat shields. The AK-47’s dark finish is a result of it being soaked or treated in a finishing solution. Its wooden parts, on the other hand, are merely sanded and treated with wood stain.

The butt stock has a metal base plate and a small hole for the cleaning kit. Today, however, accessories and polymer furniture are available online.

Some AK-47’s, like those manufactured in China, have furniture made of bakelite, an orange colored industrial plastic.

How It Comes Apart

Via Wired.

Via Wired.

To disassemble an AK-47 for cleaning or accesorizing, first detach the magazine.

Pull back the bolt to clear the chamber of a leftover 7.62mmx39mm round. (Never clean a firearm when loaded.)

Set the fire selector to full automatic so it doesn’t obstruct the removal of the dust cover. (This is optional.)

Press on the button behind the dust cover–this is the recoil spring–then raise the dust cover. The button is right above the stock.

Push the recoil spring forward then pull it out of the bolt carrier, which is the lengthiest internal part of the AK-47.

The bolt carrier has three major parts. There’s the bolt carrier, the detachable bolt underneath it that contains the firing pin, and the gas piston. When field-stripping the AK-47 these parts don’t need to be separated although the bolt should always be checked.

AK47 disassembled receiver

To check for precise measurement of parts, the author suggests consulting other sources.

Flip the handguard latch (also known as the retaining pin), not the sight, up. Pull out the gas chamber together with its wooden heatshield. The three small holes on either side of the gas chamber help discharge excess gas.

The gas chamber, along with the barrel, is protected by a wooden heat shield. Either of the heat shield’s can be pried off and re-attached when field stripping the AK-47.

The AK-47 is now disassembled. The 16.3 inch barrel doesn’t come off unless it was made to be removable. More often than not it’s permanently stuck to the trunnion.  To clean the barrel and the chamber, use the cleaning rod fixed beneath the muzzle brake.

If there is an internal problem with the AK-47 that doesn’t involve the bolt carrier, check the trigger assembly and the hammer for damage. There’s a bit of a technique to removing either part. The video below is an excellent reference.

If the problem is with the fire selector, detach the dust cover and the recoil spring with the selector switched to semi-automatic. With the recoil spring removed, pull the fire selector 180-degrees upwards in a counter-clockwise direction, then slide it out of its hole.

via Ultimak.com

Via Ultimak.com

How It Comes Together (Part 1)

Thanks to the US gun market, a huge online network for parts and information exists to inform those curious about the AK-47’s inner workings. (It’s legally imported to the US with restrictions.)

What if you had to build an AK-47 from scratch though? If this is the case, household tools won’t suffice.

The ideal “military grade” steel for a rifle barrel is always chrome molybdenum. The AK-47 begins with a 4140 steel rod 16.3 inches long. It would even be better to use 4140 steel for the whole rifle.

In lieu of 4140 steel, scrap metal from discarded cars, aircraft, and even appliances can suffice for AK-47 parts aside from the barrel. Keep in mind that any aluminum or stainless steel parts can’t be treated with anti-corrosive liquids.

AK47 Trunnion

A steel plate is also essential. This forms the receiver. With the proper dimensions and at least 1mm thick, a stamped AK-47 receiver needs to have its entry points for rivets and supporting components drilled first. When done, the receiver is set on a die and folded. At this point, legitimately manufactured AK-47’s have their serial numbers and the maker’s info engraved on the receiver.

The receiver’s two guide rails are then positioned above the opening for the magazine well. These two parts keep the magazine in place.

As shown above, the AK-47 has a front trunnion for the barrel assembly and a rear trunnion for its wooden butt stock.

To protect these same parts from rust and corrosion, they all need to be treated. In terms of assembly line production, a controlled rusting process called Bluing is what manufacturers do to give their weapons a decent finish.

For modest production lines of AK-47’s, Parkerizing is just as effective a treatment and leaves a nice finish.

Parkerizing is a process where a solution of manganese phosphate and water is applied to polished metal parts.The first stage for parkerizing is to blast the main components of the AK-47 with hot air to remove impurities.

The second stage is to dip the the components–the barrel assembly attached to the receiver plus the separated parts–in the heated parkerizing solution in a stainless steel tray (or a steam table pan) for at least 20 minutes. The barrel and gas block are sealed to protect the rifling.

The third stage is to set the parts on a separate tray until they’re ready for drying.

A different spin on parkerizing is to use a black oxide solution. The process is the same and the effect is a deeper finish for the AK-47’s metal parts.

Everything from the trigger assembly to the dust cover should undergo finishing.

How It Comes Together (Part 2)

A would-be AK-47 is a barrel assembly and a stamped receiver bent to its desired “U” shape.

A completed barrel is one that’s been bored and rifled, which is when grooves have been threaded inside the barrel to set the round on its trajectory. When a proper gun drilling machine is unavailable, either a lathe and a drill press shall suffice

The barrel of an AK-47 is part of an assembly that includes the front sight, the gas block, the [rear] sight mounted on its block, the cleaning rod, and the metal locks to secure the heat shields.

Each of these can be fitted using a hydraulic press.

The barrel assembly then fits into the trunnion.

AK47 Hydraulic Press

Hydraulic Press

The completed barrel assembly is then connected to the receiver. This is done by fitting the trunnion to the front of the receiver and fastening it with rivets using a jig.

Keep in mind that the hammer, the trigger assembly and the magazine catch are all fitted into the receiver with rivets. Some AK-47 owners choose screws over rivets, but rivets are stronger.

With the barrel assembly secured to the receiver, the gas chamber is set between the sight block and the gas block. The wooden heat shields are then put in place to protect the shooter’s hand when firing.

The fixed wooden butt stock is screwed to the rear trunnion. Smaller screws secure the metal plate that meets the shoulder and if the capsule for the tool kit is available, slide it inside its hole. The pistol grip is also screwed in place behind the trigger assembly.

AK-47 receiver interior

The bolt, containing the firing pin, is then installed underneath the bolt carrier and the piston. This assembly enters through the sight block and occupies the gas chamber. The recoil spring then slides into the bolt carrier until most of it is inside, with its nub (or button) aligned with the dust cover, which is the last part to be attached.

The AK-47 is complete. To test the rifle, one simply pulls the bolt and squeezes the trigger. A hollow click should indicate it works. Time for the range, perhaps?

Shoot!

AK-47 Type 56

Chinese-made Type-56 AK-47 clone. Note the slightly altered barrel assembly supporting an under-folding bayonet. The pistol grip and the front sight (it’s rounded rather than crescent shaped) are also different.

The AK-47 is a semi-automatic assault rifle with a rotating bolt system. This means whenever a round is fired, the bolt slides backward, rolling out the spent round’s shell. As it slides forward it catches a new round from the magazine and secures it into the chamber.

This action is produced by the 7.62mm round’s propellant gas as it exits the barrel. While some of the gas is discharged by the muzzle brake, some of it also travels up the gas block and into the gas chamber, pushing the piston and the bolt carrier backward, hence “[it] rolls out the spent round’s shell. As [the bolt] slides forward it catches a new round from the magazine and secures it into the chamber.”

AK47 Elysium

On paper, the AK-47 has a range of 300 meters. Yet for most of its operating history, the AK-47 was and is often used in battles with distances less than 100 meters.

When used by a properly trained individual, a well-maintained AK-47’s shots may exceed its optimal range and strike targets beyond 400 meters.

The AK-47 isn’t stuck in the past either. Depending on available gear and tooling, the basic rifle supports an under-barrel grenade launcher, several muzzle brakes, rifled grenades, optics, fore grips, any type of folding stock from steel to bakelite, and different chambered barrels to fire NATO rounds.

Old enough to collect a pension, the AK-47 in the right hands can still surprise the world.

1919-2013

Mikhail Kalashnikov (1919-2013)

 

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